chore: code cleanup

src/Routing/DateParam.php

@@ -0,0 +1,31 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Routing;
+
+/**
+ * The Y-m-d day identifier that every board route speaks.
+ */
+final class DateParam
+{
+    /** Route requirement, so a malformed day 404s instead of silently falling back to today. */
+    public const PATTERN = '\d{4}-\d{2}-\d{2}';
+
+    public static function parse(?string $value): ?\DateTimeImmutable
+    {
+        if (null === $value || '' === $value) {
+            return null;
+        }
+
+        // The leading "!" resets the time part, so the result is midnight rather than "now".
+        $date = \DateTimeImmutable::createFromFormat('!Y-m-d', $value);
+
+        return false === $date ? null : $date;
+    }
+
+    public static function parseOrToday(?string $value): \DateTimeImmutable
+    {
+        return self::parse($value) ?? new \DateTimeImmutable('today');
+    }
+}